Pump pressure control system



April 3, 1956 Filed Nov. 13 1.95]

N. PLANK PUMP PRESSURE CONTROL SYSTEM 2 ShetsSheet 1 H. Plank.

His Arforneg April 3, 1956 N. PLANK 2,740,357

PUMP PRESSURE CONTROL SYSTEM Filed NOV. 13, 1951 2 Sheets-Sheet 2\nvenhar: N. Pkmk By- His ArTorneg United States Patent PUMP PRESSURECONTROL SYSTEM Norris Plank, East Chicago, Ind, assignor toShellDeve'lopment Company, Emeryville, Calih, a-corporation of DelawareApplication November 13,1951, Serial No. 256,085 7 Claims. (Cl. .10337)This invention relates to the control of pumps and pertains moreparticularly to a control system for readily varying the over-allcapacity of a reciprocating pump without loss of efficiency.

Reciprocating plunger pumps are presently used instead of centrifugalpumps in many large pipe line pumping stations because of the greaterefficiency realized. When constant-speed electric motors are used todrive the reciprocating pumps, the operator encounters the difficultproblem of varying the capacity of the pump in a simple manner withoutexcessive loss of efliciency.

At present, motor-driven reciprocating pipe line pumps may be controlledby (1) providing speed variation of the pump, (2) mechanically varyingthe stroke of the pump operating at a fixed speed, or ('3) by by-passingliquid from the discharge end to the suction end of the pump. All of theabove-mentioned methods are subject to important drawbacks; the firstand second methods are very expensive in that they require theinstallation of additional equipment while the last-named method is veryineflicient as the pump uses the same amount of power while pumpinglesser quantities of liquid.

it is therefore a primary object of the present invention to provide apump control system whereby the capacity of a reciprocating pump may bevaried over a considerable range without loss of efliciency.

Another object of the present invention is to provide a pump controlsystem whereby the maximum discharge pressure and minimum suctionpressure of 'a reciprocating pump may be set at any desired value.

A further object of this invention is to provide a pump control systemfor a reciprocating pump driven by a constant speed motor whereby themaximum discharge pressure and/or the minimum suction pressure may bere-set or varied when the pump is in operation.

Another object of this invention is to provide a pump control systemcapable of effectively eliminating substantially all pressure surges onthe discharge side of a reciprocating plunger pump.

These and other objects of this invention will be understood from thefollowing description taken with reference to the attached drawing,wherein:

Figures 1 and 2 are diagrammatic views, partly in crosssection,illustrating two arrangements of the present pump control system.

A portion of a reciprocating plungerpump 11 is shown in Figure l whichincludes a pump housing 12 having mounted for reciprocating therein oneor more plungers 13. Any suitable type of pressure-tight packing may bearranged around the plunger, such for example as a plurality of packingrings 14 and a follower ring 15 held in place by a gland 16.

The pump barrel 17 communicates with a discharge conduit 18 through apassageway 19, discharge check valve 20 and passageway '21. Similarly,the pump barrel 17 is in communication through passageway 22, suctioncheck valve 23 and passageway 24 with suction pipe line 25. The openingof valves 20 and 23 is limited by adjustable valve plugs 68 and 69screw-threaded into the housing 12.

Additionally, the pump barrel 17 is also in communication, throughpassageway 26 and conduit 27, witha fluid-pressure responsive device 28.The pressure responsive device 28 comprisesa closed tank or housingformed by apair of flanged vessels .29 and 30 in face-to-facerelationship on either side of a plate 31 whichdivides the housing intoclosed fluid-tight chambers 32 and33.

The plate 31 forms the central support plate of a damping device ordiaphragm means and has formed thereon or attached on either sidethereof a pair of raised annular walls or 'fianges 34 and 35-upon whicha pair of flexible diaphragms 36 and 37 are positioned or secured inspaced relationship so as to form fluid-tight compartments 38 and 39 onopposite sides of the plate 31. The diaphragms 36 and 37 may be made ofany flexible material, such as, for example, rubber, rubberized canvas,sheet metal, or the like, which may be secured in any suitable manner,as by clamping, cementing, soldering, etc., to the flanges 34 and 35. Inthis embodiment the -diaphragms 36 and 37 are clamped between theflanges 34 and 35 andrings 49 and 41, respectively.

A hole is formed through the center of the transverse plate 31 and ashort tubular member 42 fixedly secured therein, as by welding.'Mountedfor axial movement in the bore 49 of tubular member 42 is avalve stem 43. Secured to the valve stem 43cm opposite sides of saidplate 31 and spaced therefrom are suitable valve-closure means, such,for example, as beveled valve plates-45 and 46, formed so as to fittightly against the beveled valve seats 47 and 48 around the edges ofthe hole 49 when forced thereagainst. A more .positive seal between thevalves and their seats may be secured by the use of rubber ring seals 50and 51 suitably secured to the valve plates. The overall length of thevalve stem 43 including the thickness of plates 45 and 46 is preferablychosen so that the distance between the centers of the diaphragms 36 and37 is equal to that at the peripheries. Both compartments 38'and 39 ofthe diaphragm assembly are filled with any suitable clean fluid such asoil, said fluid being relatively incompressible, of reasonably constantviscosity at operating temperatures andhaving a low freezing point.

The upper diaphragm 36 is secured to the valve stem 43 between valveplate 45 and a diaphragm contact disk 52 which is in turnfixedlypositioned on stem 43 by a nut 53. In a like manner the lower diaphragm37 is secured between valve plate 46 and a second diaphragm contact disk54 which is held in place by a nut 55. If desired, the ends of the valvestem 43 may be slidably mounted and aligned in tubular members orperforate cage members56 and 57 aflixed, as by welding, to the innerwalls of the vessels 29 and 30. The two vessels 29 and '30 are securedtogether in a fluid-tight manner on opposite sides of the plate 31 inany suitable manner, as by bolts While one chamber 33 of the pressureresponsive device 28 is in open communication with the pump barrel 17through conduits 26 and 27, the other chamber preferably communicatesthrough a port 59 and conduit 60 with a large container of high pressurefluid, for-example, a gas reservoir 61. The pump barrei 17 may alsocommunicate at the same time, through conduits 22 and 62, with onepressure chamber of a second pressure responsive device 63 which isidentical in construction with the onehereinabove described with regardto numeral 2%. The second chamber in the Vessel 63 is in communicationthrough conduit 64 with a second large container of pressure fluid, suchas a gas bottle or tank 65. The tanks 6i. and

'65 preferably have a volume substantially greater, preferably 2 to 10times greater, than the chambers 32 and similar chamber in device 63 sothat compression of the pressure fluid within the system issubstantially elimiline 18 is more than 1000 lbs.

forces liquid into chamber 33 at a pressure greater than nated. Thereservoir tanks 61 and 65 in turn may be each in communication throughconduits 70 and 71 and valves 72 and '73 with a pressure cylinder 74 or75 by which the two systems (i. e. the chambers 32 and 33 and twosimilar chambers in the second pressure responsive device 63 and theircommunicating tanks 61 and 65) may be charged to predeterminedpressures. If desired, the

tanks 61 and 65 may be covered with insulation or buried Assuming, forexample, that the minimum suction and maximum discharge pressures of thepump 11 were to be 50 and 1000 p. s. i., respectively, tanks 65' and 61would be precharged with gas from cylinders 75 and 74 to discharge gasat those pressures into the pressure chambers 63 and 28.

At any time when the fluid pressure in the pump discharge line 18 isbelow 1000 p. s. i., the pressure within the pump barrel 17 and itscommunicating chamber 33 would also drop to below 1000 p. s. i. Thus,with 1000 p. s. i. gas pressure being exerted on top of diaphragm 36while a lesser pressure is acting on the lower side of diaphragm 37,both diaphragms 36 and 37 are moved downwardly until the valve plate 45seats on the beveled valve seat 47 preventing any further flow of fluidfrom chamber 38 to chamber 39 between the diaphragms 36 and 37.

As long as the discharge pressure of the pump remained below 1000 p. s.i., the valve 45 would remain seated on its seat 47 and no movement ofthe diaphragms 36 and 37 would take place. pressure rises for somereason above 1000 p. s. i., the present pump control unitoperates tovary the capacity of the pump in the following manner.

As the pump plunger moves downwardly and the pressure in the pump barrel1'7 exceeds 1000 p. s. i., fluid will be forced into the lower chamber33 of the pressure unit 28 rather than out through valve 20 if thepressure in Since the plunger 13 1000 lbs., this pressure fluid actsagainst the lower side of diaphragm 37 to move both diaphragms 36 and 37and valve stem 43 upwardly until valve plate 46 seats in its seat 48, asshown in Figure l of the drawing.

Preferably, the pressure responsive unit is of a size that thediaphragms 36 and 37 displace an amount of fluid equal to that displacedby one stroke of the pump, say, from 2 to 5 gallons in pipe line pumps.Thus, if the pump discharge pressure was above 1000 lbs. during theentire stroke, the lower chamber of the pressure unit 28 would acceptall the fluid discharged by the pump for that stroke. As the plunger 13withdrew from the pump barrel on its suction stroke, the pressure withinthe pump barrel 17 would drop and the fluid which was previously forcedfrom the pump barrel 17 to the chamber 33 by the plunger, would beforced from the chamber 33 back into the pump barrel 17 by the gaspressure of 1000 lbs. acting on the top of diaphragm 36. Thus, as longas the pressure in the discharge pipe line 18 or the pump dischargepressure remains above 1000 lbs., the fluid on each stroke of the pumpis shuttled back and forth between the pump barrel 17 and pressurechamber 33.

It may, therefore, be seen that when the fluid transmitting or retainingcapacity of the pressure chamber 33 equals the displacement of the pumpplunger 13, the acceptance of liquid by the pressure chamber 33 com-However, if the pump discharge- 4 pletely offsets the plungerdisplacement in the pump and hydraulically nullifies the action of thepump plunger stroke entirely. On the other hand, a pressure unit 28 of acapacity which would accept 50 percent of the plunger displacement inits pressure chamber 33 would hydraulically shorten the pump stroke by50 per cent.

It may be seen that pressure unit 28 is designed to receive fluidpressure surges from the pump 11 rather than allowing them to betransmitted through the discharge line 18. The construction of thepressure unit 28 prevents pressure surges or excessive pressures fromdamaging the unit. When a 1000 lb. pressure is being exerted on the topdiaphragm 36, a pressure greater than 1000 lbs. applied to the lowerface of diaphragm 37 causes both diaphragms to .rnove upwardly forcingfluid from compartment 39 through the bore 49 of tubular member 42 andinto compartment 38. A continued increase in pressure on diaphragm 37causes valve plate 46 to seat in its seat 48 thus closing the flowchannel 49 and stopping the flow of fluid from compartment 39 tocompartment 38 whereby the diaphragm 37 is protected from being rupturedby increased pressure within chamber 33.

The rate at which the valves 45 and 46 open and the diaphragms 36 and 37are flexed between their extreme positions depends upon the rate oftransfer of fluid between compartments 38 and 39 through bore 49. Thebore 49 is preferably of a size which prevents a too rapid transfer offluid so that the diaphragms are protected against rupture and yet of asize suflicient to permit the entire transfer of fluid during thesuction stroke of the pump 11.

A second pressure unit 63 connected into the suction side of the pump 11between the pump barrel 17 and the intake valve 23 operates to vary thecapacity of the pump it the suction pressure upstream to the intakevalve 23 is less than a predetermined value, say 50 p. s. i. Since thenormal operating pressure of the pump 11 is above 50 pounds, anexcessive amount of fluid (the amount displaced by one stroke of theplunger 13) is normally.

contained in the lower chamber of the pressure unit 63. Whenever thesuction pressure upstream of theintake valve 23 is less than 50 lbs.,the diaphragm unit within the pressure unit 63 feeds liquid back to thepump barrel. This same liquid is forced back and forth between the pumpbarrel 17 and the pressure unit 63, thus effectively hydraulicallyshortening the stroke of the plunger. As in the case of pressure unit28, the fluid receiving and transmitting capacity of pressure unit 63 ispreferably equal to the fluid displaced by one stroke of the pumpplunger 13.

From the foregoing description it may be seen that comprises frictionallosses involvedin the fluid flow between the pressure chambers and thepump barrel. The high efficiency realized by the present pump controlsystem is due to the fact that the power used in pushing the diaphragmsin one direction (against the gas reservoir pressure) is only stored,being returned to the pump on the suction stroke by the gas pressurefrom the reservoir pushing the diaphragms in the opposite directionwhich forces fluid back into the pump barrel to help raise the pumppiston.

An advantage of the present pump control system is that the maximum pumpdischarge pressure and/or the minimum intake pressure may be readilyvaried at any time, even when the pump is in operation, by simply 1pressure chambers -chamberscontrolling either the intake or dischargepreschanging the pressure in tanks 61 and 65 so that more or lessfluidpressure'is applied to the diaphragms in the pressure units. Whilethe present pump control system hasibeen described when applied to apump l'lhaving a single piston 13, 'it is realized that the controlsystem '.may also "be utilized for controlling duplex or triplex "pumps,or a pumphaving any desired number of pistons,

single-acting or "double-acting. If either the maximum discharge pumppressure or the minimum intake pressure is "to "be controlled, aseparatepressure chamber such as 28 or 63 must be in open communicationwith each pump barrel or working end thereof. If both the discharge andintake pressures of the pump are to be controlled,

it is necessarytha'ttwo pressure chambers, such as 28 and 63, beconnected in open communication with each pump barrel 17. Thus, ifboththe discharge and intake j pressures of a triplex single-acting pumpareto be controlled, -it would be necessary to employ a total of six 28.However, all three pressure pressure vessel-80 comprises a fluid-tighttank divided into three pressure chambers 82, 83 and 84 by transverseplates 85 and 86. The plates 85 and 86 are identical in design to plate31 of Figure 1 and form the central plates of two diaphragm units.

The upper diaphragm unit comprises a pair of diaphragms 87 and 88secured to and movable with a valve stem 89 and valve plates 90 and 91.Similarly the lower diaphragm unit comprises diaphragms 92 and 93, valvestem 94, and valve plates 95 and 96. One chamber, for example the upperchamber 82, may be in communication through conduit 97 with a highpressure bottle 98 while the lower chamber 84 is connected to a lowpressure bottle 99 through conduit 100. The bottles 98 and 99 may bepre-charged from pressure bottles in a manner similar to that describedwith regard to Figure 1.

The chamber 83 in the pressure vessel intermediate the two diaphragmunits is in open communication at all times with the pump barrel 101. Inthe following example it is assumed that the pressure fluid is beingdischarged from the high and low pressure bottles 98 and 99 at pressuresof 1000 and 50 p. s. i. When the pressure in the pump barrel 101 exceeds1000 p. s. i., fluid is forced by the plunger 102 from the barrel 101through conduit 106 into the central chamber 83 of the pressure vessel80. The diaphragms 87 and 88 are forced upwardly against the 1000 p. s.i. pressure fluid from the bottle 98 until valve 91 is closed, as shown.On the suction stroke the excess fluid pumped to chamber 83 is withdrawninto the pump barrel 101. As soon as the discharge pressure of the pumpdrops below 1000 p. s. i. this fluid is pumped out the pump dischargevalve 103 into the discharge pipe line 104. At that time the valves 90and 95 of the two diaphragm units are closed.

In the event that the intake pump pressure upstream of its intake valve105 drops below 50 p. s. i., the 50 p. s. i. pressure fluid acting ondiaphragm 93 causes valve 95 to open, forcing fluid from chamber 83 intothe pump barrel 101. On the discharge stroke of the pump, this fluid isreturned to the chamber 83. The 1000 p. s. i. pressure fluid acting ondiaphragm 87 at this time is ineflective as valve 90 has been closedpreventing any further movement of the diaphragms 87 and 88.

I claim as my invention:

1. A displacement pump control system comprising in combination with apump having at least one pump barrel and a plunger reciprocatingtherein, a closed vessel, diaphragm means fixedly mounted in said vesseldividing said chambers comprising two spaceddiaphragms, rigid platemeans fixedly connected within the housing parallel to said diaphragmsand dividing the space therebetween into two fluid-tight compartmentsadapted to contain a pressure fluid, fluid conduit means through saidplate means in communication between said compartments and valve meansin said conduit means for stopping the flow of fluid therethrough whenthediaphragms are at their extreme position of travel in eitherdirection.

2. A displacement pumpcontrol system comprising in combination with apump having at least one pump barrel and a plunger reciprocatingtherein, a closed vessel, a wall member dividing said vessel into twochambers, said wall member having an opening therethrough, flexiblepartition "elements aflixed about said opening on either side of saidwall member to form a fluid-tight variable-volume compartment withineach of said chambers, said compartments being in communication witheach other-through said opening, an outside fluid pressure source, andfluid .conduit means comprising orifices through the walls of saidvesselincommunication between said vessel, .saidpressure'source and saidpump to apply the pressure of said source to one of the chambers in saidvessel and the pump barrel pressure to the other chamber, said pressuresbeing applied to said chambers exteriorly of the variable-volumecompartments therein.

3. A displacement pump control system comprising in combination with apump having at least one pump barrel and a plunger reciprocatingtherein, a pair of closed vessels, a wall member dividing each vesselinto two chambers, said wall member having an opening therethrough,flexible partition elements aflixed about said opening on either side ofsaid wall member to form a fluid-tight variable-volume compartmentwithin each of said chambers, said compartments being in communicationwith each other through said opening, an outside source of a high and alow pressure fluid, and fluid conduit means comprising orifices throughthe walls of said vessels in communication between said vessel, saidsource of pressure fluids and said pump to apply the high pressure fluidto one of the chambers in one vessel, the low pressure fluid to one ofthe chambers of the other vessel and the pump barrel pressure to thesecond chamber of both vessels, said pressures being applied to saidchambers exteriorly of the variable-volume compartments therein.

4. A displacement pump control system comprising in combination with apump having at least one pump barrel and a plunger reciprocatingtherein, a closed vessel, a wall member dividing said'vessel into twochambers, said wall member having an opening therethrough, flexiblepartition elements aflixed about said opening on either side of saidwall member to form a fluid-tight variable-volume compartment withineach of said chambers, said compartments being in communication witheach other through said opening, a rod member extending through saidopening and attached at each end to one of said flexible partitions tomaintain a fixed spacing therebetween, valve means carried by said rod,said valve means being adapted to close said opening, an outside fluidpressure source, and fluid conduit means comprising orifices through thewalls or" said vessel in communication between said vessel said pressuresource and said pump to apply the pressure of said source to one of thechambers in said vessel and'the pump barrel pressure to the otherchamber, said pressure being applied to said chambers exteriorly of thevariablevolume compartments therein.

5. A displacement pump control system comprising in combination with apump having at least one pump barrel and a plunger reciprocatingtherein, a pair of closed vessels, a wall member dividing each vesselinto two chambers, said wall member having an opening therethrough,flexible partition elements affixed about said opening on either side ofsaid wall member to form a fluid-tight variable-volume compartmentwithin each of said chambers, said compartments being in communicationwith each other through said opening, a rod member extending throughsaid opening and attached at each end to one of said flexible partitionsto maintain a fixed spacing therebetween, valve means carried by saidrod, said valve means being adapted to close said opening, an outsidesource of a high and a low pressure fluid, a first fluid conduit incommunication between said high pressure source and one of the chambersin one vessel, a second fluid conduit in communication between said lowpressure source and one of the chambers in the other vessel, and a thirdfluid conduit in communication between said pump barrel and the secondchamber of both said vessels.

6. The device of claim including valve means in said first and secondfluid conduits whereby the pressure from said high and low pressurefluid sources may be varied to adjust the minimum intake pressure andmaximum discharge pressure of the pump to any desired value.

7. A displacement pump control system comprising in combination with apump having at least one pump barrel and a plunger reciprocatingtherein, a closed vessel, a pair of diaphragm assemblies spaced parallelto each other dividing said vessel into three fluid-tight variablevolumefluid-tight chambers, plate means positionedon either side of saiddiaphragm assemblies limiting the movement thereof, an outside source ofa high anda low pressure fluid, fluid conduit means incommunicationbetween the center chamber of said fluid-tight vessel andthe pump for applying the pump barrel pressure tov said chamber, aconduit in communication between thehigh pressure fluid source and oneof the end chambers of said vessel and a second conduit in communicationbetween the low pressure fluid source and the other end chamber of saidvessel.

References Cited in the file of this patent UNITED STATES PATENTS315,485 Davies Apr. 14, 1885 684,806 Enzinger Oct. 2, 1901 910,292Krichbaum Jan. 19, 1909 1,452,223 Smith Apr. 17, 1923 1,932,921 Bizzarria--' Oct. 31, 1933 2,055,578 Hurst Sept. 29, 1936 2,265,232 Hotter Dec.9, :1941 2,517,501 Mennesson Aug, 1, 1950 2,570,965 Meyers Oct. 9, 19512,619,907 Paterson Dec. 2, 1952 2,711,697 Gibbs June 28, 1955 FOREIGNPATENTS 319,758 Italy Apr. 5, 1934

